Fix various documentation problems flagged by sphinx (#4871)

Co-authored-by: Oleg Pudeyev <[email protected]>

Author: p-mongo

source/tutorials/getting-started-rails.txt

@@ -480,7 +480,8 @@ migrating from ActiveRecord to Mongoid.
 ActiveRecord models derive from ``ApplicationRecord`` and do not have
 column definitions. Mongoid models generally have no superclass but must
 include ``Mongoid::Document``, and usually define the fields explicitly
-(but with `Dynamic Fields`_ may be used instead of explicit field definition).
+(but :ref:`dynamic fields <dynamic-fields>` may also be used instead of
+explicit field definitions).
 
 For example, a barebones Post model may look like this in ActiveRecord:
 

source/tutorials/mongoid-configuration.txt

@@ -598,7 +598,7 @@ Puma
 
 Use the ``on_worker_boot`` hook to reconnect clients in the workers and
 the ``before_fork`` hook to close clients in the parent process
-(`Puma documentation <<https://puma.io/puma/>`_):
+(`Puma documentation <https://puma.io/puma/>`_):
 
 .. code-block:: ruby
 
@@ -684,9 +684,9 @@ In development, some settings can be adjusted to provide a better developer
 experience.
 
 - ``:server_selection_timeout``: set this to a low value (e.g., ``1``)
-if your MongoDB server is running locally and you start it manually. A low
-server selection timeout will cause the driver to fail quickly when there is
-no server running.
+  if your MongoDB server is running locally and you start it manually. A low
+  server selection timeout will cause the driver to fail quickly when there is
+  no server running.
 
 Sample recommended development configuration:
 

source/tutorials/mongoid-documents.txt

@@ -745,6 +745,8 @@ to encode symbol values as strings, include the following code snippet in your p
   end
 
 
+.. _dynamic-fields:
+
 Dynamic Fields
 ==============
 

source/tutorials/mongoid-relations.txt

@@ -182,6 +182,7 @@ The following examle illustrates the difference between ``exists?`` and
 ``any?``:
 
 .. code-block:: ruby
+
   band = Band.create!
   # Member is not persisted.
   band.members.build
@@ -384,7 +385,7 @@ Thanks to MongoDB's document model, Mongoid also offers embedded associations
 which allow documents of different types to be stored hierarchically
 in the same collection. Embedded associations are defined using
 ``embeds_one``, ``embeds_many`` and ``embedded_in`` macros, plus
-``recursively_embeds_one`` and ``recursively_embeds_many``for recursive
+``recursively_embeds_one`` and ``recursively_embeds_many`` for recursive
 embedding.
 
 Embeds One

source/tutorials/sharding.txt

@@ -69,6 +69,8 @@ be specified:
 place of a field name, in which case Mongoid will use the foreign key
 configured in the association as the field name:
 
+.. code-block:: ruby
+
   class Person
     include Mongoid::Document